(a) Field of the Invention
The present invention relates to an aperture grill for a color cathode ray tube (CRT) having a color selection function and, more particularly, to an aperture grill for a CRT which effectively suppresses vibration, and thereby facilitates the landing of electron beams on the phosphor screen to obtain high-definition color pictures.
(b) Description of the Related Art
Generally, color CRTs are designed to reproduce the original picture image on a glass screen by receiving the picture image signals from from an external source and exciting phosphors coated on the screen with electron beams emitted from the electron gun in accordance with the signals.
In order to obtain high-definition color pictures, the electron beams should land correctly on the phosphor screen. In this regard, a color selecting shadow mask is placed directly behind the screen to ensure that each beam hits the correct phosphor. As the electron beams pass through apertures perforated on the shadow mask, the generation of spurious colors due to the excitation of the wrong phosphors can be minimized.
In recent times, a shadow mask called an aperture grill has been mainly employed to realize a high-definition color CRT. In contrast to the common shadow mask, the aperture grill has a horizontally taut mask with a plurality of slits arranged thereon. The taut mask is tightly secured to a rigid frame.
FIG. 3 is a perspective view schematically showing a conventional aperture grill. As shown in FIG. 3, the aperture grill 1 includes a mask 12a having a plurality of slits 10a, a frame 14a for accommodating the mask 12a, and a springs 16a for mounting the frame 14a on the inside of a panel of the color CRT.
The mask 12a is taut in at least one direction and tightly secured to the frame 14a. The frame 14a has a rigid structure sufficient for bearing the tensional strength of the mask 12a.
Meanwhile, the common shadow mask is easily thermally expanded when electron beams impinge thereon. This phenomenon is usually called a doming defect of the shadow mask. But, in the aforementioned aperture grill 1, the doming defect can be minimized because the mask 12a is taut and tightly secured to the frame 14a.
Nevertheless, in order to obtain the high-definition color pictures, a critical problem should be resolved in the aperture grill 1. The problem is that: the aperture grill 1 severely vibrates during operation of the color CRT because the slit formation elements are thin metal strings susceptible to vibration even by resonant waves from the speaker mounted within the color television.
Therefore, a plurality of damping wires 18a are conventionally provided on the mask 12a in the lengthwise direction to suppress or damp the vibration of the slit formation elements. However, this approach does not effectively overcome this drawback.